This invention relates to an opening and closing device for cord operated closures and particularly to one utilizing a unidirectional motor. Most prior devices required a bi-directional motor to cause the cord to be driven in opposite directions. In one instance, as shown in U.S. Pat. No. 2,468,453, a unidirectional motor is used, but the entire motor is pivotally mounted and moved by solenoids to change the motor shaft engagement with the cord operating mechanism for changing closure direction.
In most instances where an automatic shutoff is used, switches are provided which had to be actuated by mechanisms attached directly to the cord. The current invention moves the cords for the closure device by means of a pair of idler pulleys mounted on a pivotal pulley housing which is used to manually move the idler pulleys into and out of engagement with a frictional drive roller, with the closure cords pinched therebetween, one idler pulley moving one cord in one direction and the other idler pulley moving the other cord in the opposite direction. The frictional drive roller is unidirectionally driven by a unidirectional motor.
The two cord engaging idler pulleys are designed to permit each pulley to pivot toward both cords of the closure mechanism but to drive only one cord at a time. The idler pulleys are formed in two sections, one section to engage the cord, the other section to guide the other cord. The idler pulleys are mounted within a common pivotal housing such that the idler pulley which engages which cord is determined by the direction of pivoting the housing.
The device includes an automatic shutoff in the form of a tension responsive release means. When the driven cord has caused the closure to travel the full extent of its capability, the tension in the cord is effective to operate the shutoff and release the cord. In the exemplary embodiment, the drive mechanism is slidably mounted upon a frame such that tension in the cord will cause the drive mechanism to slide upon the frame and engage a release cam to move the pulley housing and both of the idler pulleys mounted thereon, thereby releasing the cord. Return springs return the mechanism to the initial released position.
Additionally, the device incorporates a manual release device to enable the user to stop the closure movement at any time before the closure reaches the end of its travel. The manual release device is a levered cam to engage and slidably move the drive mechanism upon the frame to then engage the automatic release cam discussed above.
Other objects, features and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings.